// GenericsNote: Converted.
/*
 *  Copyright 2001-2004 The Apache Software Foundation
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.apache.commons.collections15.functors;

import java.io.Serializable;
import java.util.Map;

import org.apache.commons.collections15.Transformer;

/**
 * Transformer implementation that returns the value held in a specified map
 * using the input parameter as a key.
 *
 * @author Matt Hall, John Watkinson, Stephen Colebourne
 * @version $Revision: 1.1 $ $Date: 2005/10/11 17:05:24 $
 * @since Commons Collections 3.0
 */
public final class MapTransformer<I, O>
		implements Transformer<I, O>, Serializable {

	/**
	 * Serial version UID
	 */
	static final long serialVersionUID = 862391807045468939L;

	/**
	 * The map of data to lookup in
	 */
	private final Map<I, O> iMap;

	/**
	 * Factory to create the transformer.
	 * <p/>
	 * If the map is null, a transformer that always returns null is returned.
	 *
	 * @param map
	 *            the map, not cloned
	 * @return the transformer
	 */
	public static <I, O> Transformer<I, O> getInstance(Map<I, O> map) {
		if (map == null) {
			return ConstantTransformer.NULL_INSTANCE;
		}
		return new MapTransformer<I, O>(map);
	}

	/**
	 * Constructor that performs no validation. Use <code>getInstance</code> if
	 * you want that.
	 *
	 * @param map
	 *            the map to use for lookup, not cloned
	 */
	private MapTransformer(Map<I, O> map) {
		super();
		iMap = map;
	}

	/**
	 * Transforms the input to result by looking it up in a <code>Map</code>.
	 *
	 * @param input
	 *            the input object to transform
	 * @return the transformed result
	 */
	@Override
	public O transform(I input) {
		return iMap.get(input);
	}

	/**
	 * Gets the map to lookup in.
	 *
	 * @return the map
	 * @since Commons Collections 3.1
	 */
	public Map<I, O> getMap() {
		return iMap;
	}

}
